Bosch LBB 1925-10 User Manual
Communications Systems | LBB 1925/10 Plena System Pre-Amplifier
LBB 1925/10 Plena System Pre-Amplifier
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u Six-zone system pre-amplifier, with single or dual
channel operation
u Two input channels for call stations
u Universal input for microphone/line, with speech
optimized tone control
u Three inputs for BGM selection and music optimized
tone control
u Front panel zone selection for BGM and call station
zone selection for calls
The Plena system pre-amplifier is a versatile, highperformance unit with call and mono BGM
(background music). It fulfills a wide variety of public
address requirements at a surprisingly low cost. It can
provide dual channel operation for simultaneous calls
and BGM for up to six different zones, using two Plena
amplifiers.
Functions
The call channel provides two inputs for the Plena call
stations, LBB 1941/00 (all-call) or LBB 1946/00 (sixzone), with loop-through capability, and universal,
balanced input. One is a 3-pin XLR connector for
microphone or line level (selectable), and the other is
a 5-pin DIN-connector with all‑call priority contact,
which may also be used to start one of the available
chime attention signals.
The microphone input has a selectable speech filter
for improved intelligibility, a volume control, and bass
and treble tone controls with shelving characteristics
optimized for speech. The call channel is available on
the balanced XLR master output.
The BGM channel provides three inputs on stereo
cinch-connectors, converted to mono, with front panel
selection, volume control and bass and treble tone
controls with shelving characteristics optimized for
music. The BGM channel has a direct output on
balanced XLR for dual channel operation. It can also
feed the master output, with the lowest priority, for
single channel operation. Zone selector switches on
the front panel control the BGM routing. An overload
protected 24 VDC output provides power for driving
external relays, often making an external power supply
unnecessary.
An emergency/telephone input with signal level
detector (VOX) and volume preset has the highest
priority to all zones. Two trigger inputs (contact
closure) activate alarm or time signals to pre-selected
zones. Many different chime tones are available. A PC
audio input with RS-232 control provides software
controlled zone configuration, or automatic messaging
in combination with the LBB 1965/00 Plena Message
Manager. There are six levels of priority available for
BGM, microphone, call stations, trigger inputs and
emergency input. A set of relays directs the amplifier
output(s) to different loudspeaker groups (zone
switching).
2 | LBB 1925/10 Plena System Pre-Amplifier
Each zone has a tri-state control on the front panel
that can turn it off, switch it to the call channel, or to
the BGM channel. The all‑call microphone input and
emergency activation override the call station
selection on the call channel. Each zone has separate
priority overrides with preset volume levels. This
assures an appropriate message volume, independent
of any local volume settings, such as for BGM. Both
three‑wire and four‑wire override schemes are
supported. An override also activates a voltage-free
contact (call-active) available for external control and
monitoring. The master output channel, or one of the
input channels, can be monitored through the
headphone connector and/or the LED VU‑meter.
Controls and indicators
Front
• LED power meter
• Power on LED
• Call active LED
• Three knobs for mic/line volume, treble, and bass
levels
• Three knobs for BGM volume, treble, and bass levels
• BGM source selection knob
• Six zone-selections keys
• Six zone status LEDs
• On/off switch
Back
• EMG input volume control
• Mains voltage switch
Interconnections
Front
• Headphone jack
Back
• One (DIN or XLR) Mic/line input
• Two (DIN/DIN) call station inputs
• PC audio (cinch) input
• Priority input
• Master (XLR) output
• BGM (XLR) output
• Emergency signal input
• Two trigger inputs
• RS-232 (DE-9)
• Three (cinch) CD, tape, aux inputs
• Six 100 V speaker outputs
• 24 VDC output
• 24 VDC input
• Three control inputs
• Ground screw
• IEC mains socket
Certifications and approvals
Safety acc. to EN 60065
Immunity acc. to EN 55103-2
Emission acc. to EN 55103-1
Region Certification
Europe CE
Installation/configuration notes
LBB 1925/10 rear view
Parts included
Quantity Component
1 LBB 1925/10 PLENA System Pre-amplifier
1 Power cord
1 Set of 19”mounting brackets
1 Plena CD
1 Installation and User Instructions
Technical specifications
Electrical
Mains power supply
Voltage 230/115VAC, ±15%, 50/60 Hz
Current inrush 230/115 VAC, 1.5/3 A
Max power consumption 25 VA
Battery power supply
Voltage 24 VDC, +10% / -15%
Current max 1 A
Performance
Frequency response 50 Hz to 20 kHz (+1 / -3 dB)
Distortion <0.5%
Bass control ±10 dB @ 100 Hz
Treble control ±10 dB @ 10 kHz
Channel separation >70 dB @ 1 kHz
Priority mute >40 dB
Dynamic range 100 dB
Mic/line input 1 x
Connectors 5‑pin DIN, 3‑pin XLR, balanced, with
phantom power
Sensitivity 1 mV (mic), 200 mV (line)
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